Geodetic longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is measured in degrees, with the prime meridian at Greenwich in London serving as the reference line, designated as 0 degrees. Longitude values range from 0 to 180 degrees east or west of the prime meridian. Longitude is essential for navigation and mapping, helping to pinpoint locations accurately. It works in conjunction with geodetic latitude, which measures north-south positions. Together, these coordinates form a grid system that allows for precise identification of any location on Earth.